The present invention relates to a converter for an electric motor or a transformer and more particularly but not exclusively a converter for a motor that is asynchronous or synchronous, that has permanent magnets, or that operates on DC.
The term xe2x80x9cconverterxe2x80x9d is used to cover inverters and drives, i.e. any static semiconductor apparatus enabling an electric motor to be controlled or frequency to be changed when feeding an electric transformer.
Converters are known that comprise electronic cards received in a box fixed on the motor.
The drawback of such known converters is that in the event of an electronic failure, it is necessary to replace the entire box, which means that the box must be separated from the motor.
Furthermore, each box is specific to a given motor which gives rise to relatively high manufacturing costs when a motor is made in a short manufacturing run only.
The invention seeks to provide a novel converter which makes it possible in particular to replace faulty electronic cards easily.
Another object of the invention is to reduce the cost price of the converter.
The invention achieves this by the fact that the converter comprises a connection box having passages for electrical conductors, and a semiconductor electronic module releasably fixed to the connection box, said electronic module comprising a radiator-forming box that is open at one end, at least one electronic card that is at least partially embedded in a resin cast into the inside of said radiator-forming box, and at least one connector emerging from the resin, the opening of the radiator-forming box being arranged in such a manner as to enable it to be fitted to the connection box, the connection box having at least one window giving access to the connector(s) of the electronic module.
By means of the invention, the electronic module of the converter can easily be replaced without it being necessary to separate the connection box from the electric motor or transformer on which it is fixed.
Furthermore, electrical connections can easily be established by the user when the radiator-forming box and the connection box are fixed to each other by means of the access window provided in the connection box.
Furthermore, the fact that the electronic card(s) of the electronic module is/are embedded in a resin cast into the inside of the radiator-forming box guarantees that the electronic module is reliable and electrically insulated.
Advantageously, the said resin is thermally conductive, so as to improve dissipation of heat from the electronic module.
The invention also makes it possible to achieve savings of scale in the manufacture of the radiator-forming box and in the manufacture of the electronic cards it contains since it is the connection box which serves as the interface and which needs to be fitted to different types of motor.
In other words, it is possible to make different types of connection box all arranged to receive the same type of radiator-forming box.
In a particular embodiment, the connection box includes means for fixing to a motor or a transformer.
Advantageously, the converter includes a thermally insulating gasket at the interface between the radiator-forming box and the connection box.
This insulating gasket ensures that when the motor is operating at low speed so that its cooling fan is turning relatively slowly, the heat given off by the motor is not conducted to the electronic module and does not affect the operation thereof.
Advantageously, the electronic module has one or more electronic power components mounted on the rear face of a card and in thermal contact with the inside face of the rear wall of the radiator-forming box.
Preferably, the inside face of the rear wall of the radiator-forming box has portions in relief arranged to co-operate with the above-mentioned electronic power component(s) so as to facilitate positioning of the electronic card(s) relative to the radiator-forming box.
Advantageously, the electronic module has a card carrying at least one connector for providing electric connection between the converter and electric wires conveying control signals, and also preferably but not necessarily a connector for supplying power and a connector for connection to the motor or the transformer.
Also advantageously, when the electronic module has a plurality of electronic cards, most of the bulky components of the electronic module are mounted on those faces of the electronic cards which face towards the middle of the radiator-forming box, thereby making it possible for the structure to be more compact.
Advantageously, on at least one face, the radiator-forming box has fins in the form of discontinuous parallel ribs creating ranks of ribs in two mutually perpendicular directions, with air being able to flow between the fins in each of the two directions.
Disposing the fins in this way makes it possible to guarantee cooling by convection in two different orientations of the converter relative to the vertical.
Each fin is preferably oblong in cross-section, with two opposite main faces converging towards the tip of the fin.
This shape makes it easy to provide fins that are longer or shorter depending on the power to be dissipated.
The fins are advantageously made using a mold that has one or more interchangeable slides that are selected depending on the length to be given to the fins.
This avoids the need to use a special mold for making fins of different lengths, since the fins can be made to the desired length by selecting the appropriate slide(s).
In addition, the fins remain relatively short and they harden quite quickly, thereby making high rates of throughput possible with injection molding.
The invention also provides an electric machine, e.g. an electric motor, including a converter as defined above.